The integrated approach of carbon capture, utilization, and storage via CO2 mineralization for the removal of fly ash, bottom ash, and exhaust gas-A case study of circulating fluidized bed combustion.

Despite efforts to reduce dependence on coal-fired power generation due to climate concerns, continued usage for energy stability is anticipated. This study was conducted to address environmental issues associated with coal-fired power generation and promote its persistent utilization. we aimed to establish both eco-friendly and economically sustainable practices by mitigating waste such as fly ash (FA) and bottom ash (BA) emissions while recycling them in circulating fluidized bed combustion (CFBC). Initially, we conducted a literature review to analyze the global and domestic trends in coal-fired power generation. Subsequently, we performed experimental research on CO2 crystallization as a multifaceted approach for treating exhaust gases and waste materials such as FA and BA simultaneously. Throughout this research, we implemented a simple process to ensure scalability. In the context of carbon capture, utilization, and storage (CCUS) technology, we conducted experimental research on mineralizing CO2 targeting FA and BA by applying ambient temperature, atmospheric pressure, and simulated exhaust gas. The empirical findings demonstrated that 12.28 kg CO2/ton and 58.14 kg CO2/ton of CO2 were immobilized for BA and FA, respectively. The economic evaluation was measured based on the experimental results obtained from the techno-economic analysis (TEA). The B/C ratio stands at 1.07, with the cost of composite carbonate estimated at USD 159.6 per ton. With an internal rate of return (IRR) of 7.78 % and a net present value (NPV) of USD 7294.59, the economic viability demonstrates considerable promise. Ultimately, this study aims to mitigate the impact of coal-fired power plants on climate change and enhance environmental sustainability through CO2 removal and waste recycling.

Fluorine-functionalized reduced graphene oxide-TiO2 nanocomposites: A new application approach for efficient photocatalytic disinfection and algicidal effect.

Using surface functionalization and related applications to 2D materials as innovative solutions to environmental pollution has gained considerable attention among researchers. Fluorinated graphene has derivative-based synergistic components with high thermal and chemical stability because of its structure and bonding. Fluorine-functionalized reduced graphene oxide (rFGO-TiO2) demonstrated enhanced hydrophilicity and wettability, highly efficient photocatalytic disinfection, and an algicidal effect. This study presents the hydrothermal synthesis of rFGO-TiO2 to realize antibacterial properties with high stability, which was conducted against the gram-negative bacteria Escherichia coli. To optimize antibacterial performance, the effects of multiple synthetic conditions were investigated. The antibacterial performance was optimized at an rFGO content of 1 wt%, hydrothermal temperature of 200 °C, and hydrothermal time of 1 h. The rFGO-TiO2 composite demonstrated an antibacterial efficiency of 5.76 log under ultraviolet A irradiation for 10 min and around 2 log under visible light. In the absence of light, rFGO-TiO2 took 6 h to reach an antibacterial efficiency of 6 log. Increasing the rFGO content and hydrothermal temperature beyond the optimal conditions reduced the antibacterial efficiency because of the excess rFGO and disruption of rFGO-TiO2 binding. Measurements with electron spin resonance spectroscopy confirmed that hydroxyl radicals and superoxide ions caused stress and damaged the membrane of a cell, which led to cell death.

Long-term and stable antimicrobial properties of immobilized Ni/TiO2 nanocomposites against Escherichia coli, Legionella thermalis, and MS2 bacteriophage.

Nickel has been extensively used as a high work function metal because of its abundance, low cost, relatively non-toxic nature, and environmentally benign characteristics. However, it has rarely been extended in a form of immobilized composite, which is a practical strategy applicable for photocatalytic antimicrobial activities. In this study, a composite of nickel and TiO2 (Ni/TiO2) was prepared using a photodeposition method, and its antibacterial properties were investigated using Escherichia coli (E. coli). To optimize Ni/TiO2 synthesis, the effect of various photodeposition conditions on antibacterial performance were investigated, such as the light irradiation time, metal content, TiO2 crystalline structure, and presence or absence of electron donors (i.e., methanol). The optimized 2 wt% Ni/TiO2 exhibited an antibacterial efficiency of 3.74 log within 7 min, which is more than 10-fold higher than that of pristine TiO2 (2.54 log). Based on this optimized weight ratio, Ni/TiO2 was immobilized on a steel mesh using an electrospray/thermal compression method, and its antibacterial performance was further assessed against E. coli, MS2 bacteriophage virus (MS2 phage), and a common pulmonary pathogen (Legionella thermalis, L. thermalis). Within 70 min, all target microorganisms achieved an inactivation that exceeded 4 log. Furthermore, the long-term stability and sustainable usability of the Ni/TiO2 mesh were confirmed by performing more than 50 antibacterial evaluation cycles using E. coli. The results of this study facilitate the successful utilization of immobilized Ni/TiO2 mesh in water disinfection applications.

Quantitative evaluation of the antibacterial factors of ZnO nanorod arrays under dark conditions: Physical and chemical effects on Escherichia coli inactivation.

Although zinc oxide nanorod (ZnO NR) arrays are a nanomaterial that offers efficient bactericidal activity, they have not been systematically evaluated to quantitatively investigate their disinfection mechanism under dark conditions. In this study, ZnO NR arrays of different lengths (0.5-4 µm) were uniformly grown via hydrothermal synthesis. The longer arrays exhibited higher Escherichia coli (E. coli) inactivation efficiency up to 94.2% even under darkness for 30 min. When the NR arrays were coated via Al2O3 atomic layer deposition, the inactivation efficiency was decreased to 56.4% because the generation of reactive oxygen species (ROS) and the leaching of Zn2+ ions were both hindered by the surficial coverage of defect sites. The morphological effect, i.e., the mechanical rupture of E. coli on the surface, contributed 56.4% of the bactericidal efficiency; chemical effects, i.e., ROS formation and zinc ion release, contributed the remaining 37.8% under dark conditions. The bactericidal effect of fabricated ZnO NR arrays was further validated in bottled and pond water spiked with E. coli, exhibiting 87.5% and 80.4% inactivation efficiencies, respectively, within 30 min. Understanding these antibacterial mechanisms is not only of significance for research in this and related fields but also beneficial for potential application in various fields, e.g., biomedical and antifouling areas.